During cardiac surgery, access to the coronary vasculature and the heart requires incision through the pericardial sac (i.e., pericardium), which envelops and isolates the heart from the chest walls and surrounding internal organs (e.g. lungs). As a direct result of the surgical trauma, fibrin networks connect apposing tissue surfaces and form extensive, dense and cohesive post-operative fibrous adhesions. Adhesion formation between the heart and the sternum after cardiac surgery places the heart at risk of catastrophic injury during re-entry for a subsequent procedure.
For example, a pericardial window is a common cardiac surgical procedure whereby the surgeon creates a fistula (or “window”) between the pericardial space and the pleural cavity to allow drainage of pericardial effusion (commonly known as “fluid around the heart”). An untreated pericardial effusion can lead to cardiac tamponade and death. A pericardial window involves the excision of a portion of the pericardium, which allows for the continuous draining of the pericardial effusion to the peritoneum or chest cavity, where the fluid is not as dangerous. Once the surgery is complete, the chest cavity is closed, but the incision in the pericardium may be loosely closed or left open. In either case, due to post-surgical edema, the incision usually becomes an oval opening. During the healing process, the flaps of the pericardium adhere to (“scar down”) the chest wall, lungs, epicardium and other adjacent tissues and organs, creating post-operative fibrous adhesions.
To gain access to the coronary vasculature and the heart, a surgeon may perform a median sternotomy. During a sternotomy, a vertical inline incision is made along the sternum and the sternum itself is subsequently divided. Such a procedure results in trauma in and around the tissue surrounding the sternum putting the patient at risk for complications arising from slow or impaired sternal wound healing. Sternal nonunion as the result of cardiac intervention or trauma remains a morbid condition with serious sequelae. Furthermore, adhesion formation after cardiac surgery is a well-documented, significant complication encountered during secondary procedures. Adhesion removal, while essential, is a tedious and risky process that can increase the time of an operation by 60 minutes or more. Sternal re-entry and dissection of post-operative cardiac adhesions can expose a patient to critical risks, such as injury to the innominate vein and aorto-coronary bypass grafts. Prevention of adhesions and the treatment of surgical sites remain a challenge. In recent years, bioresorbable anti-adhesion barriers have replaced non-biodegradable synthetic materials (e.g., fine surgical steel wire mesh). However, there remains a need in the art for a safe, effective means of adhesion prevention in an around the pericardium and heart after cardiac surgery using a human birth tissue construct as well as a safe, effective means of wound healing and adhesion prevention in an around surgical sites such as those resulting from a pericardial window or median sternotomy.